In construction, the process of forming elevated floors or ceilings in buildings involves pouring concrete into formwork, suspending the concrete and allowing the concrete to cure to form the floor or ceiling slabs. The formwork may be initially supported in an elevated position by any number of methods, including the use of support props. It is typically desirable to remove the formwork once the concrete hardens to a sufficient degree and continues to cure, so the formwork can be reused elsewhere. In this case, the support props are maintained in position to support the concrete for the remainder of the curing process. The support props are held tightly between the curing concrete and a supporting surface underneath (such as the floor of a lower level) during these initial stages of curing.
In most ceiling and floor constructions, reinforced, pre-stressed concrete is used. One method of pre-stressing concrete is post tensioning. This involves the positioning of tensioning tendons across the formwork (preferably in a pre-stressed manner) before concrete is poured, and then tensioning and anchoring the tendons to the periphery of the concrete once it has hardened to a sufficient degree.
Pre-stressed concrete contracts as it fully cures. As such, if the elevated concrete is supported by support props held tightly against the concrete, then as the concrete cures it will move away from the support surface of each prop. This will loosen the connection between the concrete and support prop and in most cases the contact between the support prop and concrete will be lost before the end of the curing process. Firstly, this can cause the prop to lose balance and fall. Support props are generally long, heavy members made of heavy weight steel or similar strong, rigid materials. As such, the loosening of the connection between the support prop and the concrete presents a serious safety hazard to workers and other personnel. In a typical construction site, there may be hundreds of props distributed across the floor to provide support for multiple slabs further exacerbating this safety issue. Also, the loosening of the connection also means the concrete is no longer being sufficiently supported during the entire curing process, leading to potential damage or weakening of the concrete.
Efforts have been made to alleviate these issues. However, no effective solution has been conceived or widely adopted to date. For example, one technique used in construction to reduce the safety risk is to suspend ropes between walls for catching falling props. This technique often leads to the creation of safety paths within which the workers and personnel are encouraged to walk. The process of suspending ropes can be very time consuming and laborious. Also, this method does not solve the issue of losing support during the final stages of curing and having safety zone restrictions is frustrating to workers and personnel who want to navigate freely through the site.
Another technique used involves screwing the support surface of each prop to the concrete. But this technique also comes with its own problems. As the concrete contracts the prop will be pulled up and lifted with it. This prevents the prop from falling but can damage the concrete and is a known cause for concrete cancer, for example. The process of screwing the prop to the concrete slab is also laborious and time consuming, especially when multiple props are required to support a single slab. Removing the screws afterwards can also damage the concrete. Finally, once the prop is lifted, it is no longer supporting the concrete and instead applying a load during the final stages which is in complete contradiction to the intended purpose. Sometimes, workers are required to place another support block underneath the lifted prop to maintain support, but again this is a time consuming task that cannot be performed without some delay, meaning support to the concrete slab is inconsistent and non-optimal.
It is an object of the present invention to provide an improved device and method that ameliorates at least some of the shortcomings of existing systems and methods used to support curing elevated concrete slabs in construction as described above, or to at least provide the public with a useful choice.